1. Field of Invention
The present invention relates to artificial submerged structures, and in particular to a new and unique underwater wellhead protection system for sheltering a submerged, permanently or temporarily abandoned wellhead utilizing a sloped structure configured to prevent nets, anchors, and the like from entangling or otherwise damaging the wellhead.
The exemplary embodiment of the present invention is in the form of a pyramidal structure which is designed to rest on the sea floor, enveloping the wellhead. The present invention is prefabricated and designed to be assembled on the vessel above the well site before installation on the sea floor.
The interior structure of the present invention is designed to be "self centering", and when used in conjunction with the temporary abandonment cap, the unit centers itself as it is lowered over the wellhead, thereby facilitating faster and more cost efficient installation.
The wellhead protector is designed to protect the wellhead from any anchoring, trawling or related activities, as well as protecting any nets or the like from becoming damaged due to entanglement with the wellhead.
Anchoring means is also disclosed for providing a firm placement of the shelter relative the wellhead in those cases where large anchors, oyster dredges, trawl boards and the like might tend to knock over the structure.
In addition to the protection structure, the present invention further includes a new and unique temporary abandonment cap for preventing debris from entering the wellbore. The cap is designed to be used in conjunction with the wellhead protection structure, thereby providing optimal protection for the temporarily abandoned wellhead, and assuring future reinstitution of production, should production ever be desired.
The present invention also includes a new and unique method of fabricating and installing an underwater wellhead protector in which the structure is prefabricated at the plant site, transported to the area to be deployed, assembled on site, and lowered to the sea floor after the area has been cleared of debris.
2. Prior Art & General Background
Offshore oilfield drilling is a heavily regulated industry, replete with procedural guidelines regarding safety, environmental regulations, and other concerns. One of the many areas regulated relates to the procedure for the abandonment of subsea wells.
The U.S. government has recently passed legislation and regulations dictating the proper procedure for abandoning a wellhead to insure that the well has in fact exhausted its ability to extract the resource, that the abandoned well will not pose a hazard to the environment, and that the abandoned well structure will not interfere with operations of commerce such as commercial fishing, navigation, and the like.
In accordance with these goals, the government, in its Code of Federal Regulations and U.S. Coast Guard Regulations, has dictated that abandoned subsea wells must be plugged and cleared from the sea floor such that all wellheads, casings, pilings, and other obstructions are removed to a depth of at least fifteen (15) feet below the mud line. 30 CFR Section 250.112
One can easily appreciate the great difficulties and expenses associated with the removal of subsea wellheads, conductor pipe, and casing below the surface of the seabed, especially at significant sea depths.
Fortunately, the above regulation continues on to read that the requirement for removing subsea wellheads or other obstructions may be reduced or eliminated when the wellheads or other obstructions do not constitute a hazard to other users of the seabed; id.
Thus, in accordance with the above regulations, if one were to modify the wellhead area so that it would not constitute a hazard to other users of the seabed, then presumably the necessity of removing the wellhead and casing to fifteen (15) feet below the mud line could be dispensed with. This presumption has been verified with the authorities.
Therefore, a structure enveloping the wellhead and configured so as not to pose an "obstruction" to other users of the seabed could in many cases be implemented in lieu of the expensive process of removal of the wellhead and casing below the mudline.
With regard to the temporary abandonment of wellheads, 30 CFR 250.113 states in pertinent part that "subsea wellheads, casing stubs, or other obstructions above the seabed remaining after temporary abandonment will be protected in such a manner as to allow commercial fisheries gear to pass over the structure without damage to the structure or the fishing gear".
Again, the implementation of a structure enveloping the wellhead and configured so as not to pose an "obstruction" to other users of the seabed could be implemented in lieu of the removal of the wellhead and casing.
A review of the prior art indicates that there has been little if any innovation with regard to structures designed to house and protect an abandoned subsea wellhead, let alone a structure providing means to allow commercial fishing gear such as trawls, anchors, and the like to pass over the wellhead without damage to the gear or the wellhead. The present invention provides such a structure, configuring the area around the wellhead so as not to be an obstruction to users of the seabed.
A list of prior patents which may be of interest is provided below:
______________________________________ Patent No. Patentee(s) Issue Date ______________________________________ 4,452,312 Roblin June 5, 1984 4,323,118 Bergmann Apr. 6, 1982 3,543,846 Smith Dec. 1, 1970 3,516,489 Jergins June 23, 1970 3,063,500 Logan Nov. 13, 1962 1,721,805 Cormier July 23, 1929 ______________________________________
As may be ascertained by a review of the above patents, the prior art does not teach a structural device or method for sheltering permanently or temporarily abandoned subsea wellheads, while being configured so as not to interfere with users of the sea bed such as commercial fisherman and the like.
Further, the prior art does not teach a modular subsea shelter unit which is prefabricated and thereby assembled in the field just prior to installation.
The prior art also does not disclose a subsea wellhead shelter having self-centering means of installation, nor does it teach a new and unique gravity held temporary abandonment cap to be used in conjunction with the subsea wellhead shelter.
U.S. Pat. No. 3,063,500 issued 1962 and entitled "Underwater Christmas Tree Protector" teaches "an underwater housing or protector for protecting an underwater christmas tree".
This patent teaches a cylindrical shelter for underwater christmas trees for protecting the christmas tree from the corrosive effects of salt water. The shelter is in the form of a large diameter pipe driven into the sea floor, enveloping the christmas tree. In order to protect the christmas tree from corrosion, a protective oil fills the structure, thus providing a corrosion free environment for the christmas tree.
As may be ascertained by a review of the patent, the structure is obviously distinguishable from the invention made subject this application. The patent relates to a watertight, oil filled structure designed to envelope a christmas tree for corrosion prevention.
The structure as disclosed above is not suitable for the contemplated use as taught in the present invention; further, the structure is not configured in such a manner as to protect the wellhead and commercial users of the sea bottom in accordance with the Federal Regulations. Nor does the above invention teach an easily installed shelter, but rather a complicated, extensive scheme to prevent saltwater corrosion of underwater christmas trees.
Indeed, the configuration of the above structure invites the entanglement of trawls, nets, or the like which might pass over it. The main body of the structure is in the same cylindrical, vertical form as the naked wellhead, and thus provides little utility or opportunity for use under the federal guidelines discussed above. The elongated rods implemented in a horizontal sloping form above the shelter as disclosed in FIG. 4 would not prove effective in preventing nets, anchors, etc., from becoming entangled in the structure and would in fact invite entanglement.
U.S. Pat. No. 3,543,846 issued 1970 and entitled "Underwater Oil or Gas Facility" teaches a reinforced concrete underwater structure of a frustoconical configuration and having the capability of serving as an underwater production, oil-gas separation facility, or storage facility.
The principal embodiment of the above patent teaches a rather large underwater structure, essentially serving as an underwater production platform. The exemplary embodiment appears to be the height of a 15 story building, and figures in the patent show personnel operating equipment therein.
Again, the present invention is obviously distinguishable from the above patent. The similarity of the general configuration of the two structures is the only pertinent trait. The patent does not teach an easily implemented, cost effective wellhead shelter and method of isolating the wellhead such that is does not pose a hinderance to navigation or commerce as disclosed in the present invention and is thus readily distinguishable.
Thus, based upon the above and foregoing, one can readily ascertain that the searched for invention has not been anticipated in the prior art.